Hydraulic pit prop arrangements

ABSTRACT

A HYDRAULIC PIT PROP ARRANGEMENT, THE PIT PROPS OF WHICH MAKE UP UNITS AT THE WORKING FACE AND AT A STOWING FACE, THESE UNITS BEING AUTOMATICALLY ADVANCED BY MEANS OF AT LEAST ONE THRUST RAM MECHANISM, WHEREIN THE PIT PROP UNIT ARE COMBINED INTO STRUCTURES HAVING UNITS OPERATIVE AT THE WORKING FACE AND AT THE STOWING SIDE, AND THESE STRUCTURES ARE ASSOCIATED IN GROUPS UNDER THE CONTROL OF TWO CONTROL CIRCUITS, A MAIN CONTROL CIRCUIT WHEREBY THE WORKING FACE UNITS WITHIN A GROUP ARE AUTOMATICALLY ADVANCED IN ACCORDANCE WITH THE CHANGING CONTOURS OF THE WORKING FACE AND A SUBORDINATE CONTROL CIRCUIT WHEREBY THE STOWING SIDE UNITS ARE SUCCESSIVELY ADVANCED BY THE SAME PREDETERMINED DISTANCE.

W. GOTZE HYDRAULIC PIT PROP ARRANGEMENTS Sept. 21, 1971 2 Sheets-Sheet 1 Filed Feb. 12, 1969 FIG.1

Sept. 2111971 I w GQTZE I 3,606,758

' mmnwuc PIT PROP ARRANGEMENTS 2 Sheets-Sheet 2 110,120

Filed Feb: 12 1969 G'Z 16,17 I

INVENTOR a/MAM I 0. 71614:

United States Patent Ofice 3,606,758 Patented Sept. 21, 1971 3,606,758 HYDRAULIC PIT PROP ARRANGEMENTS Wilhelm Gotze, Essen, Germany, assignor to Bergwerksverband GmbH, Essen, Germany Filed Feb. 12, 1969, Ser. No. 798,608 Claims priority, application Germany, Feb. 28, 1968, P 83 794.2 Int. Cl. E21d 15/44 US. Cl. 61-45 4 Claims ABSTRACT OF THE DISCLOSURE A hydraulic pit prop arrangement, the pit props of Which make up units at the working face and at a stowing face, these units being automatically advanced by means of at least one thrust ram mechanism, wherein the pit prop units are combined into structures having units operative at the :working face and at the stowing side, and these structures are associated in groups under the control of two control circuits, a main control circuit whereby the working face units within a group are automatically advanced in accordance with the changing contours of the working face and a subordinate control circuit whereby the stowing side units are sucessively advanced by the same predetermined distance.

BACKGROUND OF THE INVENTION In one arrangement, the pit props to be stepped forward during advance of the working face comprises units which are arranged in line behind one another. Such an arrangement clearly differs from one comprising hydraulic pit props whose units step forward alternately or leapfrog one another, since in the case of pit props of this kind the units are generally located side by side. Hydraulic pit prop units which advance on the face in follow-up fashion can, in contrast with a side-by-side arrangement, be designed in a more or less arbitrary way and in their simplest form consist of units which simply comprise a jack and a head-plate, but in more complex forms may be made up of groups of jacks.

It is already known (see 0. Jacobi Automating Face Support Structures in Order Better to Secure the Seam Roof, in the magazine Gliickauf, 101 (1965), pages 860-67), that improved support of the roof of a working requires the most rapid and complete possible underpinning of the adjacent work faces exposed at the face. In practice, this is ensured by arranging for the pit prop units or structures of two or more units to advance in relatively short but correspondingly frequent steps.

To this end, at the present state of development of the art, the pit prop units are combined into groups by a group control circuit, this group control circuit selecting and triggering the control circuits independently associated with the pit props. The individual pit prop unit control circuits in turn generally act through feelers or probes to regulate the spacing between the units and the coal face and/or the rear edge of a conveyor laid in the working. The result of this is a kind of relay-pattern advance on the part of the roof supporting arrangement since, considering any one group, although only one unit moves at a time, several units of the overall arrangement may be moving simultaneously.

This hydraulic pit prop arrangement must be regarded as the most sophisticated one at the present time, since it precludes any errors which an automatic pit prop control might introduce as a consequence of the simultaneous relaxing of several neighbouring units. It has, of course, only been applied to a pit prop arrangement in which the pit props are made up of units advancing in alternating or leapfrogging fashion, since the group control circuit can only select the individual pit prop control circuits and these in turn simply have information on the travel required, as determined by advance of the coal face or the conveyor.

The automatic advance of extractor units in a follow-up fashion, although not a groupwise operation and therefore not taking place in relay fashion, is of course known in a number of contexts (e.g. "German specification 1,182,- 184), nevertheless no superordinate control circuits are provided, so that automatic control does not preclude the possibility of error. For this reason, this kind of pit prop arrangement in mine workings is virtually out of the question and in theory at any rate can only be arranged so that considering each structure of two in-line units which is released for advance, both units step forward immediately in succession.

All the previously known kinds of automatically stepping hydraulic pit prop structures involving a plurality of units behind one another, have the common property that, even considered in individual groups, their stowing side ends are not in a straight line and in fact form a staggered pattern. If the advance of the pit prop structures is in accordance with the local and therefore irregular (considered overall) line of the coal face, then the pattern of the stowing side ends is substantially in accordance with the line of the coal face. Particularly when using the caving system, however, the stowing side ends should, for operating and safety reasons, run in a straight line at least over substantial lengths of the seam; it is only in this way that the desired breaking out of the seam roof along the back ends of the head-plates of the pit prop structure is promoted, and overloading of individual pit props and units is prevented. This kind of overloading arises, in particular, in the event that the stowing side jacks or headplates are jarned by collapsing rock. For the latter reason, long advance movements on the part of the stowing side units are desirable in order to shift these units as far as possible out of the caving zone. This, on the other hand, is in contradiction with the requirement for short and frequent steps rapidly to underpin the roof of the seam at the working face.

The invention is concerned with the technical problem of creating a hydraulic pit prop structure for mine workings, which satisfies these hitherto contradictory requirements.

SUMMARY OF THE INVENTION a superordinate control circuit the input quantity to which is a conjugate minimum spacing between the units in the structures and which causes the stowing side units to advance successively through similar distances.

Although, in this kind of pit prop structure too, a line envisaged as passing through the working face side units reproduces the line of the face since these pit prop structures are stepped forward in small steps at short intervals of time, in accordance with the area of roof exposed in each case, it is only when, in the continuous cycle operated by the group control circuit, that the units located at the face side in the group have moved away from the stowing side units to such an extent that their intervals correspond in all cases to the minimum intervals, that the stowing side units are stepped forward, these previously having been in a straight line. Since these steps forward are in each case through the same distance, once the stepping movements have been completed a straight line' at the stowing side ends is again produced. By suitably contriving the conjugate minimum intervals, it is, moreover, possible to provide an adequately long travel of the stowing side pit prop units, which is determined almost exclusively by the amount of the extension of the thrust ram mechanisms.

In practice, the minimum interval will be smaller than the maximum possible interval between the units in the pit prop structures, as deter-mined by the thrust ram mechanisms.

The measurement of the minimum interval and of the amount of advance, which is necessary for automatic control purposes, will conveniently be effected by sensing the amount of extension of the thrust ram mechanisms which produce the stepping movement.

DESCRIPTION OF DRAWINGS In the following, an example will be explained in greater detail, referring to the accompanying drawings, in which:

FIG. 1 is a plan view perpendicular to the line of the sea-m and cut away to show a working containing a hydraulic pit prop arrangement in accordance with the invention;

FIG. 2. is a circuit diagram of this hydraulic pit prop arrangement.

In a working A, coal B is being extracted using a conveyor C. Extraction is being carried out using a stowing D so that in the working a more or less straight stowing face E is obtained.

The pit prop arrangement in the working consists of hydraulic pit prop structures 1, 2, 3, 4 of identical kind. Accordingly, we need only deal with one of these structures in detail.

Each structure consists of two units 111, 1b arranged in line behind one another. These units are identical with one another.

The coal face side unit In has two props and 11, which are connected with one another through a sill plate 12. The props 10 and 11 serve to support projecting headplates 11a and 12a which have only been schematically indicated in FIG. 1. The head-plates 11a, 12a correspond to head-plates 11b on the stowing side units, the only difference being that the latter head-plates overhang to a lesser extent than those on the coal face side units.

The connection of the units in the structures is effected through the medium of a thrust ram mechanism consisting of a cylinder 13, a piston 14 and a piston rod 15. The end of the cylinder 13 and the free end of the piston rod 15 are secured to the sill plates 12 of the structures.

In the pit prop structures 1 to 4, the units 1a, 1b; 2a, 2b and so on step forward in follow-up fashion. Here, with the stowing side unit 1b fixed, the piston 14 is extended and steps the coal face side unit 1a forward, whilst if the coal face side unit 1a is fixed, operation of the thrust piston in the opposite direction causes the stowing side unit 1b to follow up.

The overall pit prop structure is split into groups. In

single group.

A group control circuit combines the coal face side units 1a, 2a, etc., in the structures 1 to 4, but has not been shown since it is well known in itself. In a specific order it selects one of the units 1a, 2a, etc., at a time. Through the medium of a control circuit incorporating appropriate regulators, and individual to each pit prop structure, the selected unit is relaxed, advanced and then fixed again, this provided that the line of advance is clear. Although only one structure at a time feeds forward in a group, nevertheless structures in different groups may move forward simultaneously.

The situation thus arising, out of the use of the control circuit described, is illustrated by way of example in FIG. 1. Because the coal face F has been broken out at F in the neighborhood of the pit prop structures 2 and 3, their units 2a and 3a have been advanced further forward than the units 1a and 4a of the neighborhood structures 1 and 4. The rock is thus underpinned throughout right up to the coal face. The position of the coal face side structures 1a, 2a, etc., follows a line corresponding substantially with the line of the coal face.

Independently of how the roof of the sea-m is underpinned at the coal face, the stowing side units 1b, 2b, 3b, 4b can move within the group constituted by the structures 1 to 4. This is effected by means of a superordinate group control circuit which selects the control circuits individual to the structures, in a specific order. This control has been schematically illustrated in FIG. 2.

An essential constituent of this group control circuit is a stepping switch arrangement 30 which can be supplied with low pressure air via a line 31 and then in a predetermined order produces pressure signals of specific duration at the outputs marked with the references of the structures 1 to 4. The control circuits individual to the structures are illustrated in FIG. 2 in simplified fashion and simply indicate the control of the stowing side units. When a signal appears at the output of the step switching arrangement 30, for example on the line 32, then a first stage control valve 33 is operated. This enables control spools 34, 37, 38 to move out of the position shown in FIG. 2. The control spool 34 controls a hydraulic high-pressure line 35 and a low-pressure line 36 so that they communicate alternately with the working spaces in the pit props 10 and 11. The control spool 37 serves to fix and relax the stowing side props 16, 17. The control spool 38 controls the thrust ram mechanism.

In the condition shown in the drawing, the coal face side props 10 and 11 of the unit 1a have been de-pressurised and are at low pressure. The cylinder space delimited by the annular surface of the piston 14 is pressurised and the props of the stowing side structure 1b are fixed. Consequently, the coal face side structure 1a can be stepped forward under a certain pressure.

The stepping forward of the coal face side units 1a to 4a has the result, in the arrangement shown in the example, that the thrust piston mechanisms 13 to 15 are extended. Each of these thrust piston mechanisms contains a control element which measures the extension. The control elements are all identical.

In the example illustrated, each control element 1'-4' consists of a tongue 40 attached to the piston rod 15 and enclosed between two strips 41.

The strips 41 are connected with the cylinder 13 in the example illustrated, whilst the tongue 40 moves between the strips and is secured to the piston rod 15.

0ne of the strips 41 in each control element contains a group of transmitter jets 42 with a compressed air connection 45. The opposite strip has a corresponding number of receiver jets 43. The receiver jets are marked I to IV. The first group of transmitter and receiver jets 42 and 43 corresponds with a hole 44 in the tongue -40.

A further group of transmitter and receiver jets, as

well as an associated hole in the tongue 40, is marked 42 to 44'.

If the coal face side unit 1a steps forward, then there is movement of the tongues 40 in the direction of the arrow shown in the drawing. The connection is supplied continuously with low-pressure air via a line 50, a distributor line 51 and lines 52 to 55. When the hole 44 passes the plane of the transmitter and receiver jets I in a control element 1 to 4, a pulse is supplied to an AND-logic element 60 made up of a total of four in-line two-way spools 61, which control the line 31 to the group control 30. The group control 30 thus only receives low pressure air and starts to operate, if the switching function at 60 is such that all the control elements within the groups have opened the I-passage and there is therefore a conjugated minimum interval on the part of all the stowing side units from the coal face side unit.

Compressed air is likewise continuously applied to the transmitter jets II to IV via the connection 45. If, with further extension of the thrust ram mechanisms, the control tongue passes these further transmitter jets, then in each case an air pulse is produced which is fed to AND-logic elements 100, 200 and 300. The transmitter jets II belong to the AND element 100, those III to the AND element 200 and those IV to the AND element 300.

A first stage control marked 400, receives the conjugated signals from the lines 101-301. With the thrust ram mechanisms operated in the reverse direction, it shuts off the pulses which would otherwise be produced by the jet groups 42, 43'. The arrangement is so contrived in this context that the pulse on the line 101 inhibits the control pulse II from the jet group 42, 43', the pulse on the line 201 does likewise in respect of the pulse III and the signal on the line 301 does likewise in respect of the pulse IV.

This kind of control thus indicates how far all the thrust ram mechanisms have extended. In the example shown, it is the smallest extension which has been travelled, namely the interval or distance I.

Accordingly, because of the pressure in the line 32, the line 70 will also carry low-pressure air so that the right-hand control jets, considering the circuit diagram of FIG. 2, will have air applied to them. The first stage valve 33 changes state with the result that, once the coal face side unit 1a has been fixed, the stowing side unit 1b follows up. In this case, the control tongue 40 is stationary whilst the strips 41 carrying the transmitter and receiver jets, are moved in the direction indicated by the arrow.

In so doing, the transmitter and receiver nozzles are passed in the order I, II, III, IV. This corresponds to the order in which the jet groups 42, 43 are passed.

The thrust ram mechanism retracts until the control jets I are once again in alignment. Then, the first stage valve can change state again because the pressure in the corresponding control line will have collapsed. In the circuit diagram of FIG. 2, it has a larger area at the right-hand side than at the left. The same process takes place in the pit prop units 2 to 4 as well. The result is that in the indicated order all the stowing side units in the group are advanced by the same amount.

The area marked 0 in the control corresponds to the interval 8, in the pit prop structure. This travel S5011 is a fraction of the maximum extended length S of the thrust ram mechanism.

The result is that as soon as all the coal face side units 1a to 4a have advanced by at least the distance S in the indicated order all the stowing side units 1b to 4b follow up. In the situation reproduced in FIG. 1, the thrust ram mechanisms of the central pit prop structures 2 and 3 have been extended by the distance S whilst the thrust, ram mechanisms of units 1 and 4 have been extended only by a fraction of this distance. Nevertheless, all the thrust ram mechanisms in the group have extended through the distance S The subject of the invention may therefore also be constituted by a method of supporting mine workings which operates in accordance with the diagram indicated.

This method of supporting mine workings is implemented by combining the pit prop structures into groups, and provides for the coal face side prop units to step forward in a specific order in accordance with the local advance on the face and therefore to follow same. The method of the invention resides in the fact that the stowing side units \1b to 4b can be stepped forward group fashion, independently of the coal face side units and in a specific order, this after achieving a certain interval 8, from the coal face side-units, the stowing side units in fact being stepped forward by an amount corresponding to this interval.

Instead of the automatic control of the stowing side units as illustrated in the drawing and described in detail hereinbefore, these units can equally well be controlled by hand. This may be advisable where extraction is carried out at a different time and different location from the roughing work.

The result of the follow-up type of mine working support arrangement illustrated, is that the stowing face E always runs in a straight line and that the follow-up step is large, so that the stowing side units 1b to 4b are not affected by rock falls from the roof of the seam.

I claim:

1. In a hydraulic pit prop arrangement comprising pit prop structures made up of pit prop units operative at the working face, pit prop units operative at a stowing side and hydraulic ram mechanisms operatively connected between the working face units and the stowing side units, which pit prop structures are operatively associated in groups; improved means for controlling advance of said structures behind the working face comprising, for each group:

a main control circuit;

face feeder means for the working face units;

switching means governed by the main control circuit in response to the feeler means selectively to operate the ram mechanisms to advance the working face units in turn so that these units follow the changing contour of the working face;

a subordinate control circuit;

sensing means responsive to the attainment of a predetermined spacing between the working face units and the stowing side units;

and further switching means governed by the subordinate control circuit in response to the sensing means selectively to operate the ram mechanisms to advance the stowing side units in succession through similar distances.

2. The improvement according to claim 1, in which the said predetermined spacing is less than the maximum extension of the ram mechanisms.

3. The improvement according to claim 2, in which the said predetermined spacing is evaluated by sensing means responsive to the degree of extension of the ram mechanisms.

4. A system for supporting mine workings by means of pit prop structures made up of pit prop units operative at the working face of the mine, pit prop units operative at a stowing side and hydraulic ram mechanisms operatively connected between the working face units and the stowing side units, which pit prop structures are operatively associated in groups, the improvement comprising, for each group:

(A) means for sensing the contour of the working face relative to the line of the working face units to produce sensing signals,

(B) means for interpreting and selectively switching said sensing signals to operate said ram mechanisms to advance the working face units in turn to cause these to follow the changing contour of the working face,

(C) means for measuring the extensions of the various ram mechanisms to produce measuring signals, and

(D) means for interpreting and selectively switching said,measuring signals to operate the ram mechanism to advance the stowing side units in succession, each through a similar predetermined distance.

8 References Cited UNITED STATES PATENTS 3,207,041 9/1965 Phillips 61-45X 3,392,531 7/1968 Ratz 61-45 3,392,532 I 7/1968 Jacobi 61-45 3,397,543 8/1968 Spies et a1. 61-45 DENNIS L. TAYLOR, Primary Examiner 

